Specific Electrochemical Surface Area Research Articles

One-step electrodeposition synthesis of NiFePS on carbon cloth as self-supported electrodes for electrochemical overall water splitting

Electrocatalytic water splitting (EWS) for hydrogen production is considered an ideal strategy for utilizing renewable energy, reducing fossil fuel consumption, and addressing environmental pollution issues. Traditional noble metal electrocatalysts have excellent performance, but their cost is high. Developing efficient, stable, and relatively inexpensive dual functional electrocatalysts is crucial for promoting large-scale EWS hydrogen production processes. Herein, a simple one-step electrodeposition method was used to grow nickel–iron phosphorus-sulfides (NiFePS) on the surface of hydrophilic treated carbon cloth (CC). The resultant NiFePS/CC with a phosphorus to sulfur ratio of 1:4 exhibited the best electrocatalytic performance, requiring only −91 mV and 216 mV overpotentials to generate the current densities of 10 mA·cm−2 in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. When it was used as a bifunctional electrocatalyst to overall water splitting (OWS), a voltage of 1.536 V can generate a current density of 10 mA·cm−2. The excellent electrocatalytic performance can be ascribed to two factors: 1) the CC with excellent conductivity serves as a growth substrate, reducing the impedance of charge transfer from the electrode to the electrolyte and accelerating the electron transfer rate; 2) The large number of ultra-thin nanosheets formed on the surface of the catalyst increase the electrochemical specific surface area, expose more reaction sites, and thus improve the electrocatalytic reaction performance. This work provides a new approach for designing efficient non-noble metal electrocatalysts for water splitting.

Identification of Suitable Mesh Size of Commercial Stainless-Steel for Electrochemical Oxygen Evolution Reaction.

The study examines the oxygen evolution reaction (OER) electrocatalytic efficiency of various stainless-steel mesh (SSM) sizes in electrolytic cells. Stainless steel is chosen due to its widespread availability and stability, making it an economically viable option. The primary objective of this investigation is to determine the optimal stainless-steel mesh size among those currently widely available on the market. The classification of stainless-steel mesh sizes as SS304 is confirmed by the minimal compositional variations observed across all mesh sizes through electron dispersive X-ray (EDX) spectra and X-ray fluorescence (XRF) analyses. Remarkably, CV experiments carried out at different scan rates indicate that SSM 200 has the maximum specific electrochemical surface area (ECSA). As a result, SSM 200 demonstrates superior performance in terms of current density response and shows the lowest overpotential in the alkaline medium compared to other stainless-steel mesh sizes. Furthermore, the SSM 200 exhibits a low overpotential of 337 mV at a current density of 10 mA/cm2 and a Tafel slope of 62.2 mV/decade, surpassing the performance of several previously reported electrodes for the OER. Stability tests conducted under constant voltage further confirm the remarkable stability of SSM 200, making it an ideal anode for electrolytic cell applications. These findings emphasize the cost-effectiveness and high stability of SSM 200, presenting intriguing possibilities for future research and advancements in this field.

Integrating Micro-Patterned Flow Fields into Electrode Architecture Via Non-Solvent Induced Phase Separation for High Performance Redox Flow Batteries

To facilitate increasing penetration of intermittent renewables in the energy mix, there is a growing need for energy storage technologies. Redox flow batteries (RFBs) have attracted significant attention in recent years due to their suitable characteristics for long-duration stationary energy storage applications. However, the wider adoption of RFB systems is still limited by the capital cost, to which the reactor stack is a large contributor[1]. Further cost reduction can be achieved by reducing kinetic, mass-transfer, and ohmic losses to improve the stack performance. Porous electrodes are key components within the battery stack, providing active sites for electrochemical reactions, and transport pathways for active species. Commercially available carbon-fiber electrode architectures include carbon paper, carbon felt, and carbon cloth. They have a highly porous structure, but their relatively low surface area and low hierarchical fiber orientation increase both electrochemical and pumping losses[2]. There is still a need to develop a low-cost porous electrode that meets the requirements of high active surface area and facile electrolyte transport to enhance battery performance and system efficiency.Non-solvent induced phase separation (NIPS) is a manufacturing route in the field of membrane technology, which is widely used to fabricate asymmetric membranes[3]. Recently this route has also been used to fabricate non-fibrous porous electrodes[4]. The microstructure of NIPS electrodes is largely influenced and controlled by the solvent/non-solvent exchange rate at the interface between a polymer solution and a coagulation bath. When the phase exchange process is slow, segregation is delayed. This type of segregation generally results in a sponge-like, relatively dense structure[5]. This sponge-like structure has the advantage of small pore size and high surface area, but also has poor hydraulic permeability and high mass-transfer losses. The trade-off between surface area and permeability needs to be further optimized.In the present study, inspired by the flow field designs widely used in RFBs to guide the electrolyte flow paths for low pressure drop, uniform electrolyte distribution, and high electrochemical performance[6], we propose a strategy to imprint micro-patterned flow fields directly into the electrode architecture during NIPS processing to improve mass transfer properties. NIPS polymer films were cast onto molds with specific micro-patterns, and the resulting micro-channels can be preserved in the electrodes after carbonization. To verify the effectiveness of the micro-patterned electrodes, here, we investigate two selected micro-patterned designs. The groove-patterned electrodes were combined with flow-through flow fields (FT-FFs) for in-plane mass transport optimization, and the pillar-patterned electrodes were combined with interdigitated flow fields (IDFFs) for through-plane flow optimizations[7]. Two geometric sizes of the micro-patterns were considered in each design. The pore sizes and distributions of the micro-patterned electrodes were determined by mercury intrusion porosimetry. The hydraulic permeability of the electrodes was evaluated by half-cell pressure drop measurements, and the electrochemical specific surface area was determined through electrochemical impedance spectroscopy under non-faradaic conditions. In addition, we performed electrochemical battery tests with symmetric iron RFB (0.5 M Fe2+/Fe3+, 2 M HCl) cells and vanadium full-cells (1.6 M V active species at 50% state-of-charge). It was found that due to the small pore size (e.g., ~1 μm) and narrow pore size distribution of the sponge-like NIPS structure, the main contribution to the total losses in electrodes without micro-patterns in electrochemical performance comes from mass-transfer. Electrodes with groove and pillar patterns can help reduce the pressure drop and improve mass transfer properties. Pillar-patterned electrodes with the combination of IDFF show high overall electrochemical performance with greatly reduced mass transport resistances. At an electrolyte velocity of 10 cm/s, the total resistances for kinetic and mass transfer are less than 0.1 Ω·cm2 in symmetric iron cell tests. Compared to the activated commercial electrode (e.g., 2-layer Freudenberg H23 carbon paper, thermally treated at 450 oC for 12 h), the total resistances for kinetic and mass transfer are reduced by ~60%, which shows great potential for adoption in next generation high-performance RFB systems. References J. Noack, L. Wietschel, N. Roznyatovskaya, K. Pinkwart, J. Tübke, Energies, 9, 627 (2016).A. Forner-Cuenca, F.Brushett, Current Opinion in Electrochemistry, 18, 113-122 (2019).H. Wang, J. Jung, J. Kim, S. Kim, E. Drioli, Y. Lee, Journal of Membrane Science, 574, 44-54 (2019).C. Wan, R. Jacquemond, Y. Chiang, K. Nijmeijer, F. Brushett, A. Forner-Cuenca, Advanced Materials, 33, 2006716 (2021).D. Wang, J. Lai, Current Opinion in Chemical Engineering, 2, 229-237 (2013).X. Ke, J. Prahl, J. Alexander, J. Wainright, T. Zawodzinski, R. Savinell, Chemical Society Reviews, 23, 8721-8743 (2018).V. Muñoz-Perales, P. García-Salaberri, A. Mularczyk, S. Ibáñez, M. Vera, A. Forner-Cuenca, ChemRxiv, (2023).

Bi2O2S topological transformation and in-situ regrowth of [hk1]-oriented SbBiS3-xSex 2D skeleton structure for construction of efficient quasi-two-dimensional Sb2S3-xSex-based heterojunction photoanodes

Antimony chalcogenides (Sb2S3-xSex), as one of the promising light-absorbing materials in optoelectronic energy storage devices, has attracted widespread attention in recent years. Of particular note, its crystal structure consists of the one-dimensional [Sb4S(Se)6]n ribbons with efficient carrier transport efficiency along the [hk1] direction. In this paper, with the aid of the topological transformation of the layered material Bi2O2S, the SbBiS3-xSex bimetallic alloy with 2D skeleton structure was induced to grow in situ, and the conversion of Sb2S3-xSex preferred orientation from [hk0] to [hk1] was realized. The corresponding results showed that 2D skeleton structure was conducive to the construction of photo traps and the increase of electrochemical specific surface area. In addition, Bi2O2S acted as an electron transport layer (ETL) to further promote the migration of photogenerated carriers. At 1.23 V vs. RHE, the photocurrent density of quasi-two-dimensional Bi2O2S/SbBiS3-xSex nanosheet photoanode was as high as 6.41 mA cm−2, which was 7.5 times that of pure Sb2S3-xSex, and the peak value of IPCE could reach 40.93%. This work undoubtedly opens up a new avenue for the designing high-efficiency antimony chalcogenides photoelectrodes.

Dual-Conductive and Stiffness-Morphing Microneedle Patch Enables Continuous In Planta Monitoring of Electrophysiological Signal and Ion Fluctuation.

The use of conductive microneedles presents a promising solution for achieving high-fidelity electrophysiological recordings with minimal impact on the interfaced tissue. However, a conventional metal-based microneedle suffers from high electrochemical impedance and mechanical mismatch. In this paper, we report a dual-conductive (i.e., both ionic and electronic conductive) and stiffness-morphing microneedle patch (DSMNP) for high-fidelity electrophysiological recordings with reduced tissue damage. The polymeric network of the DSMNP facilitates electrolyte absorption and therefore allows the transition of stiffness from 6.82 to 0.5139 N m-1. Furthermore, the nanoporous conductive polymer increases the specific electrochemical surface area after tissue penetration, resulting in an ultralow specific impedance of 893.13 Ω mm2 at 100 Hz. DSMNPs detect variation potential and action potential in real time and cation fluctuations in plants in response to environmental stimuli. After swelling, DSMNPs mechanically "lock" into biological tissues and prevent motion artifact by providing a stable interface. These results demonstrate the potential of DSMNPs for various applications in the field of plant physiology research and smart agriculture.

Fabrication of inverse opal molybdenum sulfide and its use as a catalyst for H2 evolution.

Amorphous molybdenum sulfide (MoSx) and crystalline molybdenum disulfide (MoS2) are attractive noble-metal-free electrocatalysts for the H2 evolution reaction from water. Their actual activities depend on the quantity of active sites which are exposed to the electrolyte, which in turn, is influenced by their specific electrochemical surface area. Herein we report on the fabrication of regular inverse opal MoSx and MoS2 films by employing polystyrene nanoparticles with diameters in the range of 30-90 nm as hard templates. The use of these catalysts for the H2 evolution reaction in an acidic electrolyte solution is also presented. Impacts of the regular porous structure, the film thickness as well as the chemical nature of the catalyst (MoS2versus MoSx) are discussed. It shows a catalytically-effective-thickness of ca. 300 nm where the electrolyte can fully penetrate the catalyst macropores, thus all the catalytic active sites can be exposed to the electrolyte to achieve the maximal catalytic operation.

Intensified Kirkendall effect assisted construction of double-shell hollow Cu-doped CoP nanoparticles anchored by carbon arrays for water splitting

Precisely engineering the architectures of nanoparticles (NPs) to optimize their physicochemical properties and thus electrocatalytic performances are challenging for scientists. Here, we report the controllable construction of solid, hollow, and double-shell hollow metal phosphide NPs anchored by carbon nanosheet arrays on carbon cloth. We demonstrate that Cu doping can intensify the nanoscale Kirkendall effect, which promotes the transformation from solid CuCo to double-shell hollow CoP NPs. Benefiting from its high dispersity, large electrochemical specific surface area, fast mass diffusion and good conductivity, the optimal double-shell hollow Cu-CoP-based electrocatalyst exhibits excellent activities for OER (η10 =176 mV) and water splitting (1.494 V @ 10 mA) in 1.0 M KOH with favorable stability. DFT calculations further confirm the optimized OH* adsorption energy of Cu-CoOOH/Cu-CoP due to Cu doping and interfacial synergy for boosting OER. This work provides new perspectives for engineering the nanoarchitecture of multilevel hollow NPs through the Kirkendall effect for electrocatalysis.

Fabrication of a novel Ti3C2-modified Sb-SnO2 porous electrode for electrochemical oxidation of organic pollutants

Sb-SnO2 is an appealing electrode for degrading organic pollutants in wastewater treatment, albeit further modifications are needed for its inefficient electrochemical oxidation capacity. In this work, we prepared Ti3C2-modified Sb-SnO2 electrode by electrodeposition technology. High-conductive MXene matrix regulated the Sb-Sn alloy nucleation process to decrease its domain size during deposition and generated pores during the annealing process. When introducing 20 mg MXene into the electrolyte, the obtained Sb-SnO2 electrode (Ti3C2-20) presented a larger oxygen evolution over-potential (2.32 V vsSCE), increased amount of active sites, and enlarged electrochemical specific surface area (∼4.4-fold) than the unmodified electrode, resulting in a promoted OH generation ability (∼7.4 times). Methylene blue (MB), methyl orange (MO), norfloxacin (NOR), and P-phenylenediamine (PPD) were effectively degraded by the Ti3C2-20 anode with economic energy consumption. Moreover, the Ti3C2-20 electrode also featured a longer lifetime, almost fivefold, than the unmodified Sb-SnO2 electrode due to its larger loading amount and decreased charge transfer resistance. Consequently, this work offers a new perspective for designing efficient and stable porous electrodes to address water pollution issues.

An advanced large-porosity porous channel structure electrode for vanadium redox flow batteries

Electrospinning technology has been extensively used to prepare electrodes for vanadium redox flow batteries (VRFBs). Nevertheless, electrospinning carbon nanofibers (ECNFs) electrodes suffer from low porosity and poor permeability, hence significantly hindering mass transport. To solve this critical issue, a new approach to prepare porous channel electrodes with large porosity based on electrospinning technology is proposed. The electrode is fabricated by electrospinning of polyacrylonitrile and poly (methyl methacrylate) (PMMA) solutions. PMMA not only acts as a sacrificial phase to form a porous channel structure inside the fibers, but also interconnects the fibers, which significantly increases the inter-fiber pore space and enhances the mass transfer performance. Electrochemical characterizations indicate that the electrodes have a remarkably elevated electrochemical specific surface area and outstanding electrochemical performance. Owing to the well-designed large-porosity porous channel structure of the electrode, the energy efficiency of the VRFB equipped with this electrode is 74.45% at 300 mA cm−2 and 81.03% at 200 mA cm−2, and the battery can be continuously charged and discharged for more than 1200 cycles, which demonstrates a long-term cycling stability of the electrode. All of these indicate that this efficient and durable method for propagating electrode has broad application prospects.

In-situ corrosion induced Zr-doped Ni/Fe (oxy)hydroxide layer on Ni-Fe foam realizing efficient electrocatalysis for oxygen evolution reaction

The synthesis of efficient and economical electrocatalysts for oxygen evolution reactions (OER) by the energy-saving approach has far-reaching significance for the production of hydrogen by water electrolysis. Herein, a facile route was proposed to prepare Zr-doped Ni/Fe (oxy)hydroxide layer grown on Ni-Fe foam (Zr-NiFe(OH)x/NFF) by chloride ions in-situ corrosion strategy in “NaCl-ZrOCl2” mixed solution. The smooth NFF surface was effectively transformed into a rough multimetallic (oxy)hydroxide nanosheet with high electrochemical specific surface area and strong bonding to the substrate, resulting in excellent interface performance for mass transfer and charge transfer. Specifically, the incorporation of Zr4+ regulated the electronic environment around the Ni/Fe center, as a result, adsorption energies were optimized and the inherent OER activity of active sites was enhanced. The Zr-NiFe(OH)x/NFF self-supporting electrode exhibited outstanding OER electrocatalytic activity where low overpotentials of 211 and 245 mV were obtained to achieve 10 and 100 mA cm−2 respectively, along with impressive durability for 40 h. This work provides a simple strategy for low-cost and mass production of the robust OER self-supporting electrocatalysts.

Preparation of Au/MoS2‐CNT@CNF Composite Electrocatalyst for High‐Efficiency Hydrogen Evolution Reaction

AbstractBy virtue of excellent ion storage and fast ion‐diffusion rates, molybdenum disulfide (MoS2) has been regarded as a promising electrocatalyst for hydrogen evolution reaction (HER). however, it is inherently inert to HER, its electrochemical activity is usually improved by enhancing electrical conductivity or increasing exposed active sites. To improve the conductivity and adsorption of MoS2, we prepared the MoS4‐Ppy intermediate by oxidative polymerization. Taking advantage of the adsorption properties of MoS4‐Ppy to combine with Au(III), Au(III) was simultaneously reduced to Au nanoparticles(Au NPs). Combining the Au/MoS4‐Ppy with BC and converting it into a catalyst Au/MoS2‐CNT@CNF by calcination, the catalyst activity was improved by optimizing the concentration of Au(III). Combining MoS2 with Polypyrrole (Ppy) and Bacterial cellulose (BC) not only improves the conductivity of MoS2, but also increases the exposed active sites. Notably, the obtained 50 ppm Au/MoS2‐CNT@CNFs exhibited good HER catalytic performance in an acidic electrolyte (0.5 M H2SO4) with a low overpotential of only 108 mV at a current density of 10 mA ⋅ cm−2, a low Tafel slope of 52.1 mV ⋅ dec−1, and along with outstanding stability. The improvement of electrocatalytic activity is mainly attributed to the larger electrochemical specific surface area of the composites after adsorption of Au(III) and loaded BC. The low load Au NPs can provide dense active sites. Moreover, and synergistic effect among Au NPs, MoS2, and Ppy can greatly enhance the charge transfer efficiency and lead to excellent electron transfer ability, thus significantly improving the HER performance.

Doping vacancy synergy engineering: Ce-doped FeNi-Sx micro-succulent ameliorating electrocatalytic oxygen evolution performance

The co-control strategy of doping and vacancy has proved to be an effective and flexible approach in the development of efficient catalysts because of the synergistic regulation of electronic structure and active site number. Here, we synthesized an electrocatalyst with a special micromorphology of succulent plants. In addition, the doping of the rare earth element Ce with a large ionic radius in NiFe bimetallic sulfides is accompanied by a large number of vacancies. Ion doping synergistic with vacancy engineering improves the electrochemical intrinsic performance in the OER process and has enhanced electron transfer ability and electrochemical specific surface area, thus exhibiting high electrocatalytic OER performance, small Tafel slopes, ultralow overpotential of 294 mV at 100 mA cm−2 and 276 mV at 50 mA cm−2 and robust operating durability. Combined with DFT calculations, the role of Ce ions in the NiFe bimetallic sulfide system was revealed. This work not only provides a strategy for designing ion doping to enhance vacancy concentration but also constructs an efficient and stable oxygen evolution electrocatalyst system, which provides an alternative path for designing efficient electric and photocatalysts.

One-step growth of Ni2Co(PO4)2 microspheres for high energy density supercapacitors

Nickel and cobalt phosphates as a kind of low-cost inorganic materials are promising electroactive materials. The structure stability and good dispersibility of micro-spherical materials make them popular in the energy storage field. Therefore, the fabrications of Ni–Co phosphate microspheres with some facile and cost-effective methods have attracted lots of attentions. In this work, we present one-step growth of Ni2Co(PO4)2 microspheres using urea as pH regulator. Urea decomposes into NH3 and CO2 during the hydrothermal reaction process, resulting in the precipitation of Ni–Co phosphates. The as-prepared Ni2Co(PO4)2 microspheres exhibit uniform and well-dispersed spherical morphology. Compared with traditional Ni2Co(PO4)2 particles, Ni2Co(PO4)2 microspheres exhibit larger electrochemical specific surface area and smaller resistance of electrons/ions transfer. The specific capacity of Ni2Co(PO4)2 microspheres reaches as high as 153 mAh g-1 at a current density of 1 A g-1, which is 1.59 times higher than that of traditional Ni2Co(PO4)2 particles. In addition, this facile one-step synthetic method can be applied to fabricate series of Ni–Co phosphates with different Ni/Co atomic ratios. This work provides a facile synthetic method of fabricating Ni–Co phosphate materials, which has potential applications in large-scale manufacture.

Preparation of a novel Ce and Sb co-doped SnO2 nanoflowers electrode by a two-step (hydrothermal and thermal decomposition) method for organic pollutants electrochemical degradation

Nanostructured Sb-SnO2 electrodes with high electrochemical activity and stability are urgently desired for electrochemical oxidation of refractory organics in wastewater treatment, yet hard to be controlled and synthesized. Hence, we combined the hydrothermal method and thermal decomposition technologies to prepare a novel Ce and Sb co-doped SnO2 nanoflowers electrode (Ti/Ce-Sb-SnO2NFs). The incorporation of Ce endowed the Ti/Ce-Sb-SnO2NFs anode with an increased oxygen evolution over-potential (OEP) (1.99 V vs.SCE), lower charge transfer resistance (7.54 Ω⋅cm2), large specific electrochemical active surface area (141.83), a great number of active sites and superior •OH generation ability. Consequently, nearly 100% decolorization efficiency and 91.45% chemical oxygen demand (COD) mineralization efficiency of methylene blue (MB) (20 mg/L) were achieved by the Ti/Ce-Sb-SnO2NFs anode within 90 min. Additionally, the Ti/Ce-Sb-SnO2NFs anode stability was also improved with a longer accelerated lifetime (15.5 h) than the given Ti/Sb-SnO2NFs electrode (8.2 h). We also prepared other nanostructured (nanoparticles, nanoclusters and nanosheets) Sb-SnO2 electrodes with high oxidation capacity utilizing this two-step method, which demonstrated its great versatility. Accordingly, this work could provide a new strategy for fabricating efficient and stable rare earth elements (Ce, Nd, La, etc.) and Sb co-doped SnO2 nanostructured electrodes for decomposition organic pollutants in the field of wastewater treatment.

The highly efficient electrocatalytic oxidation of 5-hydroxymethylfurfural on copper nanocrystalline/carbon hybrid catalysts: structure–function relations

The Cu species in Cu(NSD)/CP exhibit a high electrochemical specific surface area, which allows efficient transformation from Cu0and Cu1+species to Cu2+with high catalytic capacity, resulting in excellent catalytic performance (96% yield of FDCA).

Three-dimensional porous Cu2O with dendrite for efficient photocatalytic reduction of CO2 under visible light

Cuprous oxide (Cu2O) is a promising photocatalyst that can reduce CO2 to fuel under visible light irradiation. However, the fast electron-hole recombination and photo-corrosion of Cu2O limit its photocatalytic performance. In order to overcome these two shortcomings of Cu2O, in this work, three-dimensional (3D) porous Cu2O with dendrite structure was prepared by electrodeposition combined with subsequent thermal oxidation. The 3D porous Cu structure was completely transformed to Cu2O with 220℃ annealing, which exhibited high electrochemical specific surface area and good photocatalytic CO2 reduction performance. Compared with non-porous Cu2O structure, 3D porous Cu2O demonstrated 2.5 times increment of concentration of photogenerated carriers (4.3 × 1020 cm−3) and 24-fold enhancement of photocatalytic CO2 reduction to CO (13.4 nmol cm-2h−1). Especially, some C2 reduction product was observed for the 3D porous structure. This is because the 3D porous structure improves the mass transfer efficiency of CO2 gas, and the nano-sized dendrite structure enhances the efficiency of light capture and photoinduced electron transportation. Furthermore, the rapid separation and high reaction activity of photoinduced holes and electrons result in the anti-photocorrosion properties of 3D porous Cu2O. Therefore, this work not only provides new idea to address the activity and stability of Cu2O, but also develops a facile strategy for photocatalytic reduction of CO2.

High Catalytic Performance of Silver‐Doped Gold Nanocages for Methanol Electrooxidation

AbstractHollow or porous noble metal nanocrystals with large specific electrochemical surface area and stability hold stimulating technological applications in fuel cell catalysis. Here, a simple galvanic replacement reaction synthesis of Ag‐doped Au nanocages with a tunable Ag/Au atomic ratio is developed. Without surface ligands being used in the synthesis, the obtained AuAg nanocages with hollow cavity and opened nanoporous shell possess clean surface and enhanced electrocatalytic activity. In the electrocatalysis of the methanol oxidation reaction (MOR), the obtained AuAg nanocages possess high electrocatalysis properties and show morphology and composition‐dependent electrocatalytic property. The optimized AuAg cubic nanocages that have 5% Ag exhibit excellent electrocatalytic activity for MOR, and this is attributed to the unique geometric structure and the well‐controlled Ag content. The hollow and nanoporous structure can effectively promote the mass transfer and atomic utilization during the catalytic process for MOR. Density functional theory calculations indicate that introducing of a small amount of Ag facilitates methanol adsorption to the surface of catalysts and promotes the break of the OH bond during the MOR process, thus accordingly enhances the catalytic activity.

In-situ assembly of Cu/CuxO composite with CNT/Bacterial cellulose matrix as a support for efficient CO2 electroreduction reaction to CO and C2H4

A CNT/Bacterial Cellulose (BC) nanocomposite with a large surface area and conductive properties was in-situ cultivated to retain the native 3D nanofibril network. The Cu-CuxO/CNT/BC nanocomposite electrode was in-situ fabricated via reduction with the CNT/BC composite as a support, comparing KBH4 and NaBH4 as a reducing agent to obtain efficient electrodes for CO2 reduction (ECR-CO2). Both electrodes exhibited higher performance than the traditional carbon cloth or pristine BC supported Cu-based catalysts for conversion of ECR-CO2 to CO and C2H4. The CNT/BC as a support provided not only more active sites for copper catalyst but also increased the charge transfer and selective performance of C2H4 product, due to the synergistic effect of CNT and copper. The smaller honeycomb and dendritic lamellar crystal morphology of the obtained Cu-CuxO/CNT/BCNaBH4 electrode possessed a large electrochemical specific surface area, providing more active sites for ECR-CO2. The double-layer capacitance and the current density reached 11.8 mF cm−2 and 33.3 mA cm−2, respectively. At a potential of −1.5 VRHE, the Faraday efficiency (FECO + FEC2H4) was 66%. Moreover, the Cu-CuxO/CNT/BC nanocomposite electrode was very stable, and withstood tolerance in ECR-CO2 for more than 20 h. This study possibly will provide a new design for catalyst support on CNT/BC substrate to regulate advanced catalysts/electrodes for different applications, especially to ECR-CO2 in terms of higher charge transport properties, lower contact resistance, higher current density, and more stable CO2 electroreduction performance.

Influence of ionomer on the durability of Pt/C catalyst

Ionomer is an important part of the catalytic layer in proton exchange membrane fuel cell. Its main role is to conduct protons. We investigated the effect of ionomer on the durability of Pt/C catalyst using rotating disk electrode (RDE) under two modes: the real operating conditions (mode 1) and startup/shutdown conditions (mode 2). The structural changes of Pt/C catalyst after the durability test were analyzed by identical location transmission electron microscopy (IL-TEM). Results show that the addition of ionomer improved the durability of Pt/C catalysts. After the durability test of mode 1, the addition of ionomer reduced the change of half-wave potential (∆E1/2) of oxygen reduction reaction from 23 to 11 mV, which is attributed to the growth of Pt particles rather than carbon corrosion. Ionomer delayed the decrease of electrochemical specific surface area (ECSA) of Pt/C catalyst, which is beneficial to the maintenance of Pt activity. After the durability test of mode 2, in addition to the growth of platinum particles, carbon corrosion occurred in the catalyst layer, and the growth of platinum particles was mainly due to carbon corrosion. The addition of ionomer reduced the ∆E1/2 of oxygen reduction reaction from 25 to 5 mV. Furthermore, the growth of platinum particles and carbon corrosion can be clearly seen by IL-TEM, and the corrosion of the carbon support resulted in the loss and agglomeration of platinum. The average particle size of platinum in Nafion-containing catalyst increased from 2.7 to 3.76 nm, while that of Nafion-free catalyst increased from 2.44 nm to 4.19 nm.

Self-supported amorphous nickel-iron phosphorusoxides hollow spheres on Ni-Fe foam for highly efficient overall water splitting

The development of high-efficiency and economical bifunctional electrocatalysts in hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) plays a key role in overall water splitting. In this study, a success was achieved in synthesizing the hollow nanospheres with amorphous nickel-iron phosphorusoxides nanoflakes layer grown on Ni-Fe foam (NiFe-POx/NFF). Firstly, with the assistance of oxygen bubbles templates, the hollow spheres comprised of NiFe-OH nanosheets were produced through the in-situ chemical oxidation of NFF surface. After phosphorylation, crystalline NiFe-OH nanosheets were transformed into amorphous NiFe-POx with plenty of defects and disorders, thus improving the density of active sites. The catalytic performance of NiFe-POx/NFF was further improved by a combination of stable 3D hierarchical nanostructure, effective mass transport and charge transfer, as well as the electrochemical specific surface area expanded by fluffy featherlike nanoflakes. The self-supported electrode of NiFe-POx/NFF exhibited outstanding catalytic property in the presence of alkaline electrolyte, including a small overpotential of 110 and 247 mV required to achieve 50 mA cm−2 for HER and OER in 1.0 M KOH aqueous solution, respectively. As a bifunctional electrocatalyst, NiFe-POx/NFF could provide a low cell voltage of 1.52 V to reach 20 mV cm−2 under a two-electrode system as required for the occurrence of overall water electrolysis under alkaline medium, while showing extended durability under continuous electrolysis without degradation.